1. Field
Embodiments relate to a washing machine, and, more particularly, to a washing machine of an improved structure to prevent the generation of noise and vibration between a rotary shaft and a bearing.
2. Description of the Related Art
Generally, a washing machine is classified as a pulsator type washing machine that washes laundry by rotating wash water and the laundry using a pulsator rotatably installed on the bottom of the inside of a water tub, an agitator type washing machine that washes laundry by agitating wash water and the laundry using an agitator protruding from the central region of the inside of a water tub, or a drum type washing machine that washes laundry by repeatedly lifting and dropping the laundry through the rotation of a drum accommodating the laundry.
An example of such a drum type washing machine is disclosed in U.S. Pat. No. 6,510,716 providing a drum type washing machine including a water tub, a rotary tub rotatably disposed in the water tub, the rotary tub having a rotary shaft extending to the outside of the water tub, a bearing to rotatably retain the rotary shaft, and a drive motor connected to the rotary shaft at the outside of the water tub to simultaneously rotate the rotary shaft and the rotary tub.
The disclosed drum type washing machine is capable of performing a spin-drying function as well as a washing function. During spin-drying, the rotary shaft and an inner race of the bearing to retain the rotary shaft rotate at high speed, with the result that the rotary shaft and the bearing cannot rotate at the same speed. That is, there is difference in rotation speed between the rotary shaft and the bearing.
At this time, the inner race of the bearing and the outer diameter of the rotary shaft repeatedly come into contact with each other and separate from each other due to the difference in rotation speed between the rotary shaft and the bearing, with the result that there occurs a sliding phenomenon between the bearing and the rotary shaft, which generates creep noise.
Also, between an inner race of a bearing installed at the front side of the rotary shaft and a front-side step of the rotary shaft is formed a gap which causes noise and vibration.
To solve this problem, a wave washer has been used.
However, the wave washer is installed only between the inner race of the bearing installed at the front side of the rotary shaft and the front-side step of the rotary shaft, with the result that the sliding between the bearing and the rotary shaft is not fundamentally restrained, and therefore, a noise and vibration reduction effect is insignificant. In addition, a compression force is continuously applied between the inner race of the bearing and the front-side step, with the result that the wave washer is permanently deformed, and therefore, noise and vibration increase with the increase of the use time of the washing machine. Also, a frictional force providing effect, to provide a frictional force between the rotary shaft and the inner race of the bearing such that the rotary shaft and the bearing can rotate at the same speed, is insignificant. This is because, due to the shape (wave-shaped ring) of the wave washer, the frictional force is generated only at some region where the front-side step of the rotary shaft and the front side of the inner race of the bearing come into contact with the wave shape of the wave washer.